Methods of treating a surface to promote metal plating  and devices formed

ABSTRACT

Embodiments of the present invention provide methods of treating a surface of a substrate. In one embodiment a kit for carrying out the binding of metals to a substrate is provided, comprising: a container comprising a heat-resistant organic molecule derivatized with an attachment group Y and a binding group X, the binding group X promotes binding of metals; and instructional materials teaching coupling the organic molecule to the substrate by heating the molecule and/or the surface to a temperature of at least 25° C.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a divisional patent application of U.S. patentapplication Ser. No. 11/848,860 entitled “Methods of Treating a Surfaceto Promote Metal Plating and Devices Formed” filed on Aug. 31, 2007, theentire disclosure of which is hereby incorporated by reference.

TECHNICAL FIELD

The present invention generally relates to methods of treating a surfaceof a substrate, and to the use of the method and resulting films formedtherefrom in various applications such as metal plating, the protectionof surfaces against chemical attack, the manufacture of localizedconductive coatings, the manufacture of chemical sensors (for example inthe fields of chemistry and molecular biology), the manufacture ofbiomedical equipment, and the like. More specifically the presentinvention relates to methods of treating a surface to promote plating orbinding of metals, and devices formed therefrom.

BACKGROUND OF THE INVENTION

Electronic components have become smaller and thinner as the desire forsmall, thin, and lightweight devices continues to increase. This haslead to many developments in the manufacture, design and packaging ofelectronic components and integrated circuits. For example, printedcircuit boards (PCB) are widely used for packaging of integratedcircuits and devices. Current PCB substrates must provide a variety offunctions such as efficient signal transmission and power distributionto and from the integrated circuits, as well as provide effectivedissipation of heat generated by the integrated circuits duringoperation. The substrates must exhibit sufficient strength to protectthe integrated circuits from external forces such as mechanical andenvironmental stresses. As device densities increase, high densitypackage designs such as multi-layer structures are becoming increasinglyimportant, which present additional design challenges.

Polymers have emerged as a desirable material for PCB substrates.Polymer substrates exhibit advantages such as flexibility, low cost,light weight and high heat resistance, among other properties. Forexample, various polymer and carbon materials have been used such asepoxy, phenol and polyimide resins, and the like. Low end organicmaterials, such as glass reinforced epoxy, have been employed as PCBsubstrates. However, such materials exhibit poor thermal conductivityand anisotropic thermal expansion. Improved organic materials such asglass reinforced polyimide, cyanate, ester and Teflon show improvedtemperate stability, but suffer from moisture absorption and pooradhesive strength to copper.

Non-organic PCB substrates are also used. Alumina (ceramic) is widelyused and exhibits desirable thermal conductivity and coefficient ofthermal expansion (CTE), however such substrates are brittle and costly.Thus it is expected that new materials will continue to be explored aspotential candidates for PCB substrates. Irrespective of the PCBsubstrate used in a particular application, electroplating orelectro-chemical deposition techniques, particularly electrolessplating, have been widely adopted to form metallization layers on thePCB substrates. Copper has become a desired metal for metallization ofprinted circuit boards (PCB), flexible circuit boards (FCB), multi-chipmodules (MCM), and the like, as well as for semiconductor devicefabrication, because of its lower resistivity and significantly higherelectromigration resistance as compared to aluminum and good thermalconductivity. Copper electro-chemical plating systems have also beendeveloped for semiconductor fabrication of advanced interconnectstructures. These methods have involved the following two basic steps:(1) treating the surface of the non-conductive substrate with an agentto make it catalytically receptive to electrolessly formed metaldeposits; and (2) electrodepositing a metal over the electrolesslyformed conductive metal deposits. The pattern of the printed circuit isachieved through the use of screen printing or photoresist imaging. Thenon-conductive substrate may initially be copper-clad or not; but mostboards have copper cladding at the beginning of the process, which islater removed in the non-pattern areas. Such processes are,consequently, referred to as subtractive.

In the typical processes relevant to printed circuit board manufacturewherein through-hole metallization is employed, the catalytic materialmost often comprises palladium metal. The process of applying thecatalytic material to the substrate surfaces typically involves contactof the substrate with a colloidal solution of palladium and tincompounds. See, e.g., U.S. Pat. Nos. 3,011,920 and 3,532,518. It isgenerally considered that the tin compounds act as protective colloidsfor the catalytic palladium. In most cases, the catalysis of thenon-conductive substrate of the printed circuit board is followed by an“acceleration” step which exposes or increases exposure of the activecatalytic species.

Following deposition of catalyst material on the non-conductive surfacesin the manner described, the surfaces are then contacted with anelectroless metal depositing solution in which plating chemicalreduction leads to the deposit of metal from the bath onto the catalyzedsurface. The through-holes are usually plated with a copper reductionprocedure known to the art as electroless copper plating, such as thatdescribed by Clyde F. Coombs, Jr. in Printed Circuit Handbook 3rdEdition, McGraw-Hill Book Co., New York, N.Y., 1988, Chapter 12.5, whichis incorporated herein by reference in its entirety.

Methods of the type described above, while apparently simple, haveproven to be expensive and demanding of strict process controls. Furtherlimitations on the use of these processes result from the chemicalsusceptibility of the electroless metal layer and by the required use ofvery hazardous and toxic chemical agents. Efforts to overcome thesedisadvantages have met with only partial success in the past and havebrought with them their own disadvantages. Accordingly, in order toappreciate the significance of the improvements achieved by the presentinvention it will be helpful to review beforehand the main features ofcurrent printed circuit board technology.

In a typical process for the manufacture of a single- or double-sidedprinted circuit board, suitable substrates typically comprise laminatesconsisting of two or more foils of copper, which are separated from eachother by a layer of non-conductive material. The non-conductive layer orlayers are preferably an organic material such as epoxy resinimpregnated with glass fibers. Holes are drilled or punched atappropriate locations on the board, providing side-to-side connectionswhen metallized. Thereafter, the board is treated with a cleaningcomposition, typically alkaline, which removes soils and conditions thethrough-holes, followed by a slow acid etching process which is used forremoval of copper surface pretreatments, oxidation and presentation ofuniformly active copper. Typical compositions for this micro-etchingstep are persulfates and sulfuric acid-hydrogen peroxide solutions. Theboard is next catalyzed with a neutral or acid solution of tin/palladiumcatalyst, which deposits a thin layer of surface-active palladium in thethrough-holes and on the surface of the board. Colloidal tin on theboard surfaces and through-holes is removed by treatment with anaccelerator composition. The board is then ready for electroless copperplating, which is typically carried out with an alkaline chelated copperreducing solution that deposits a thin copper layer in the through holesand on the surfaces of the board. After acid-dipping, commonly withsulfuric acid, the board is metal plated with a conventional copperplating solution. It is more usual, however, to precede thismetallization step with an imaging step.

In a process known as pattern plating, a dry film photoresist islaminated to the board and then exposed to transfer the negative imageof the circuit, after which it is developed to remove the unexposedportions. The resist coats the copper that is not part of the conductorpattern. Thickness of the exposed copper pattern is increased byelectrolytic copper plating. The imaged dry film resist is then removed,exposing unwanted copper i.e. copper which is not part of the conductorpattern, and said unwanted copper is dissolved with a suitable etchant,e.g., ammoniacal copper or sulfuric acid/peroxide.

A multilayered printed circuit board is made by a similar process,except that pre-formed circuit boards are stacked on top of each otherand coated with a dielectric layer. The stack is pressed and bondedtogether under heat and pressure, after which holes are drilled andplated in the above-described manner. However, one problem present withthe manufacture of multilayer printed circuit board through-holes isthat the drilling of the holes causes resin “smear” on the exposedconductive copper metal inner layers, due to heating during the drillingoperation. The resin smear may act as an insulator between the laterplated-on metal in the through holes and these copper inner layers.Thus, this smear may result in poor electrical connections and must beremoved before the plating-on operation.

Various alkaline permanganate treatments have been used as standardmethods for desmearing surfaces of printed circuit boards, including thethrough-holes. Such permanganate treatments have been employed forreliably removing wear and drilling debris, as well as for texturing ormicro roughening the exposed epoxy resin surfaces. The latter effectsignificantly improves through-hole metallization by facilitatingadhesion to epoxy resin, at the price of roughening the copper anddecreasing the frequency response of the copper traces. Otherconventional smear removal methods have included treatment with sulfuricacid, chromic acid, and plasma desmear, which is a dry chemical methodin which boards are exposed to oxygen and fluorocarbon gases, e.g. CF4.Generally, permanganate treatments involve three different solutiontreatments used sequentially. They are (1) a solvent swell solution, (2)a permanganate desmear solution, and (3) a neutralization solution.Typically, a printed circuit board is dipped or otherwise exposed toeach solution with a deionized water rinse between each of the threetreatment solutions.

Electroplating surfaces with copper coatings is generally well known inthe industry. Typically, copper electroplating processes use a platingbath/electrolyte including positively charged copper ions in contactwith a negatively charged substrate, as a source of electrons, to plateout the copper on the charged substrate. In general, electroplatingmethods involve passing a current between two electrodes in a platingsolution where one electrode is the article to be plated. A commonplating solution would be an acid copper plating solution containing (1)a dissolved copper salt (such as copper sulfate), (2) an acidicelectrolyte (such as sulfuric acid) in an amount sufficient to impartconductivity to the bath and (3) additives (such as surfactants,brighteners, levelers and suppressants) to enhance the effectiveness andquality of plating. Descriptions of copper plating baths may be foundgenerally in U.S. Pat. Nos. 5,068,013; 5,174,886; 5,051,154; 3,876,513;and 5,068,013.

All electrochemical plating electrolytes have both inorganic and organiccompounds at low concentrations. Typical inorganics include coppersulfate (CuSO₄), sulfuric acid (H₂SO₄), and trace amounts of chloride(Cl⁻) ions. Typical organics include accelerators, suppressors, andlevelers. An accelerator is sometimes called a brightener oranti-suppressor. A suppressor may be a surfactant or wetting agent, andis sometimes called a carrier. A leveler is also called a grain refineror an over-plate inhibitor.

As described above, most electrochemical plating processes generallyrequire two steps, wherein a seed layer is first formed over the surfaceof features on the substrate (i.e. the electroless step, this processmay be performed in a separate system), and then the surfaces of thefeatures are exposed to an electrolyte solution while an electrical biasis simultaneously applied between the substrate surface (serving as acathode) and an anode positioned within the electrolyte solution (i.e.the electroplating or electrodeposition step).

The use of copper however suffers from a number of limitations. Forprinted circuit board applications, adhesion of copper to polymer PCBsubstrates is generally weak, thus requiring treatment of the surface ofthe substrate by a variety of means. For example, surface adhesion maybe enhanced by treatments such as oxidation, wet chemical treatment,plasma or UV exposure to roughen the surface of the substrate. Asmentioned above, however, one problem present with the manufacture ofmultilayer printed circuit board through-holes is that the drilling ofthe holes causes resin “smear” on the exposed conductive copper metalinner layers, due to heating during the drilling operation. The resinsmear may act as an insulator between the later plated-on metal in thethrough holes and these copper inner layers. Thus, this smear may resultin poor electrical connections and must be removed before the plating-onoperation. Prior art techniques such as different permanganatedesmearing and or neutralization compositions and methods have beentried to address this problem. For example, U.S. Pat. No. 4,073,740 toPolichette et al. discloses a composition comprising water, permanganateion and manganate ion, with a manganate/permanganate molar ratio of upto 1.2 to 1 and a pH of from 11 to 13. U.S. Pat. No. 4,515,829 toDeckart et al discloses contacting through-hole walls with an aqueousalkaline permanganate solution and thereafter a reducing agent solution.U.S. Pat. No. 4,592,852 to Courduvelis et al. teaches the use of analkaline composition to improve the adhesion of plastics to electrolessmetal deposits. U.S. Pat. No. 5,015,339 to Pendelton et al. disclosescontacting a substrate with an alkaline permanganate solution, andthereafter with a single-step permanganate neutralizer and conditionercomposition.

Other teachings in the art have suggested different approaches. Forexample, U.S. Pat. No. 4,803,097 to Fraenkel et al. discloses firstexposing the surfaces of a nonconductive substrate to an atmosphere ofozone, followed by a conditioning solvent of alcohols and strong bases,and then treatment with an oxidizing agent e.g., permanganate. U.S. Pat.No. 4,152,477 to Haruta et al. suggests etching a butadiene compositionto expose phenolic resin microcapsules in it, then sensitizing it withpalladium chloride. U.S. Pat. No. 4,448,804 to Amelio et al describestreatment with an acidic solution containing a multifunctional ioniccopolymer which has good adhesion to the substrate surface. U.S. Pat.No. 5,268,088 to Okabayashi discloses the use of alkaline adhesionpromoter solutions comprising aqueous alkali metal salts, e.g., KOH andNaOH. Glass fibers used to impregnate epoxy resin have a highly negativesurface charge and repel negatively charged tin-palladium catalystparticles. U.S. Pat. No. 4,976,990 to Bach et al. discloses conditioningagents which improve adsorption of the activating material on the glassfiber, e.g., an organic silicon compound. U.S. Pat. No. 5,342,654 toKoizume et al. discloses a method for surface roughening boards made ofpolyphenylene sulfide resin by incorporating a specific resin thereinand selectively dissolving away the specific resin at the surface.

Electroless plating systems based on palladium and tin chloridecatalysts in acidic solutions have become widely used and reported. U.S.Pat. No. 4,478,883 to Bupp et al. describes that a palladium seedingagent may be attracted to the surface of a conductive metals such ascopper, resulting in smaller amounts of the palladium catalyst going todesired areas, e.g., when plating through-holes where copper may bepresent in internal planes of the substrate. U.S. Pat. No. 4,554,182 toBupp et al. further describes replacing HCl with H₂SO₄, apparentlyeliminating a problem of resist blistering and line tailing. Effortshave been made to replace such highly acidic systems. U.S. Pat. No.4,634,468 to Gulla et al. discloses a reduced catalytic metal fixed ontoan organic suspending agent which serves as a protective colloid, and ispreferably a water soluble polymer, e.g., polyacrylamide or polyvinylpyrrolidone.

Since acidic solutions sometimes cause problems to develop in the copperlayer of laminated circuit boards, modifications of the catalytic systemhave been developed, e.g., a single step method using a variety ofdifferent pH colloidal suspensions of both the tin sensitizer and thepalladium activator, as disclosed in U.S. Pat. No. 3,011,920 to Shipley,Jr. and U.S. Pat. No. 3,532,518 to D'Ottavio. Another variation of theprocess is disclosed in U.S. Pat. No. 5,318,803 to Bickford et al.,where the catalyzing step is carried out twice, based on redox exchangereactions.

The electroless metal coating, usually copper, functions to make thethrough-holes conductive for either further electroplating, or for fullelectroless deposition to the full thickness desired, and to the fullsurface circuit pattern desired. Where the substrate is non-copper cladinitially, the function of the electroless copper is to make the surfaceconductive as well as the through-holes. The electroless plating stephas received abundant treatment in the art. U.S. Pat. No. 4,904,506 toBurnett et al. discloses electroless copper plating in which twosuccessive layers of copper are plated onto the substrate from analkaline electroless bath, the second bath having higher cyanide ion andO₂ concentrations than the first. Current trends in printed circuitboard technology indicate that smaller, higher-aspect-ratio holes willbecome the state of the art. Recently, there has been a substantialdecline in the average size of the through-hole in manufactured boards,from 0.030″ and larger, to smaller diameters. Such trends placeincreasing pressure on methodologies for producing printed circuitboards with regard to the always difficult task of properly plating thethrough-holes.

Direct plating is disclosed in U.S. Pat. No. 4,810,333 to Gulla et al.,where the non-conductive substrate is treated with an absorbed colloidsurface coating before direct electroplating is carried out. Therequirement for relatively high current densities limits this process toplating larger through-holes. Another limitation of past methods hasbeen their lack of adaptability to plating circuit board constructiontechniques now in use, which are often referred to as photoresistmethods. U.S. Pat. No. 4,089,686 to Townsend discloses such a methodusing a photopolymerizable composition. U.S. Pat. No. 4,948,707 toJohnson et al. discloses a permanent resist material employed over thecatalyst layer in a predetermined pattern. However, the layer ofcatalyzing material beneath the resist layer tends to cause currentleakage between circuit lines in close proximity to each other, e.g., inhigh density circuits. It is taught to insulate the catalyst particlesby employing a homogeneous colloidal dispersion of palladium/tinparticles, which must then be activated by application of a conventionalaccelerating solution.

The use of a post-activation or acceleration step prior to the finalstep of electro-deposition has become widespread. The purpose of thisstep is to render the activating species deposited in the activationstep as “active” as possible prior to immersing the board into theelectroless copper bath. Typically, the activating species is palladium,and in order to prevent the palladium from readily oxidizing to anonactivating form it is combined with from 1 to 10 times as many tinatoms in the stannous state. The post-activation composition, e.g., astrongly acidic or strongly basic solution, removes some of the tinatoms surrounding the palladium, thereby making greater access to thecatalyzing palladium by the electroless copper plating solution. Some ofthe tin and palladium atoms are removed and become dispersed in thepost-activation solution, where they combine to form a new and moreactive species which quickly initiates electroless deposition. Thepost-activation treatment also serves the function of solubilizing thehydroxides of tin which are formed during the rinse steps which followactivation. The hydroxides of tin form a gelatinous coating on thepalladium metal activator particles, which interfere with their properfunctioning.

The post-activation or accelerator solutions require close monitoring oftheir concentrations, treatment times and temperatures, agitation, andaccumulating levels of tin and copper, in order to avoid excess removalof tin and palladium. U.S. Pat. No. 5,342,501 to Okabavashi teaches thatan accelerator solution can also be a mildly basic or alkaline bathincorporating a small quantity of copper ions. U.S. Pat. No. 4,608,275to Kukanskis et al discloses agents which oxidize the protectivestannous tin and activate the palladium catalyst, e.g., sodium chlorite,hydrogen peroxide, potassium permanganate, and sodium perborate, andsuggests use therewith of an electroless nickel bath.

As illustrated by the foregoing, much work has been performed directedto the development and fabrication of printed circuit boards anddesigns. However, the fabrication steps are often costly andcomplicated, and improvements are thus highly sought.

Further in all applications, i.e. as a metallization layer in PCBdesigns and in semiconductor devices, copper tends to plate on localsites of nucleation, resulting in clusters of copper nuclei, copperclusters/crystal, so deposition is not uniform across the substantial orwhole surface of the substrate.

Thus, there is a need for additional developments and improvements inthe fabrication of PCB's, including for example a metal plating processthat can treat the surface of a substrate to promote advantageousbinding of metal elements on the surface, and additionally methods toplate a thin copper seed layer directly on printed circuit boardsubstrates capable of uniformly forming metal, such as copper, acrossthe substrate surface and fill features before plating of a bulk metallayer.

SUMMARY OF THE INVENTION

Broadly, embodiments of the present invention provide methods oftreating a surface of a substrate. In one particular aspect, embodimentsof the present invention provide methods of treating a surface of asubstrate that promote binding of one or more metal elements to thesurface.

In another aspect, embodiments of the present invention treat thesurface of a substrate by thermal reaction with molecules containingreactive groups in an organic solvent or aqueous solution which depositthe molecules onto or attach molecules to conductive, semi-conductiveand non-conductive surfaces or substrates.

According to some embodiments of the invention, films are formed on anyconducting, semiconductive or non-conductive surface, by thermalreaction of molecules containing reactive groups in an organic solventor in aqueous solution. The thermal reaction may be produced under avariety of conditions. Methods of the present invention produce organicfilms attached onto the surface or substrate, the thickness of which isroughly equal to or greater than one molecular monolayer.

Other embodiments of the invention generally relate to the use of thesemonolayers as a precursor for the deposition or attachment of a metallayer onto a substrate. Particularly, in some embodiments the inventionrelates to methods and systems for electrochemical deposition or platingof a metal layer on a substrate, and devices formed therefrom.

This is particularly relevant in the electroless plating of conductivemetal coatings on selected portions of a non-conductive substratesurface. The final products of these processes are particularly printedcircuit boards and related articles. In double sided and multilayerprinted circuit boards, it is necessary to provide conductive interconnection between and among the various layers of the board containingconductive circuitry. This is achieved by providing metallized,conductive through-holes in the board requiring electrical connection.The predominant prior art method of providing conductive through-holesis by electroless deposition of metal on the non-conductive throughholes drilled or punched through the board. In some embodiments methodsof the present invention relate to electroless metallization ofnon-conductive through-hole surfaces in double-sided and or multilayeroriented circuit boards. The present invention can replace prior artprocesses of the type described above, with inventive processes thatsubstitute other metallization techniques.

In some embodiments, the present invention broadly provides a printedcircuit board, comprising: at least one substrate; a layer of organicmolecules attached to the at least one substrate; and a metal layer atopsaid layer of organic molecules.

In another aspect, embodiments of the present invention provide foradditional cleaning, baking, etching, chemical oxidation or otherpre-treatment of the surface prior to the deposition or attachment ofthe molecule to enhance the deposition or attachment of the molecule,the reaction of the molecule to the surface, or the ability of thesurface to bond with the molecules as deposited.

In other aspects, embodiments of the present invention provide methodsof direct electroplating of copper on substrates without formation of acopper seed layer. Embodiments also provide structures or films oforganic molecular layers that promote favorable deposition or attachmentof metal elements onto substrates in electroplating processes.

In further aspects, a printed circuit board is provided comprising apolymer material, such as an epoxy, which may contain a substantialamount of a filler material, such as glass, silica, or other materials,modified on its surface with a chemical adhesive material, such as aporphyrin, that alters its chemical affinity for a metal, such ascopper, in order to facilitate strong adhesion between the polymercomposite and the metal layer. A second layer of the chemical adhesivelayer may be applied to the metal (copper) surface, to promote adhesionbetween it and subsequent polymer (epoxy/glass) layers. In theseembodiments, the PCB may be a multilayer conductive structure.

Of further advantage, embodiments of the present invention providemethods of selectively depositing materials on a surface or substrate byselectively contacting molecules on the surface to form regions, orpatterned regions, which are then processed to form selective areas ofcopper or other metals thereon. In this case, the adhesive molecularlayer is either contacted to specific regions of the substrate, usingphotoresist and optical lithography, as is conventionally used in theart, or it is applied to the entire surface and selectively activated.This can be accomplished by photoactivation through a lithographicprocess, ion beam activation or any other technique that can provideadequate spatial imaging of a surface.

Additionally, embodiments of the present invention provide methods offorming ordered molecule assemblies on a surface or substrate which issubsequently plated with a metal element, such as copper and the like.For example, in one illustrative embodiment, methods of the presentinvention promote metal binding to a substrate, characterized in that: asurface of a substrate is treated with an organic molecule comprised ofa thermally stable base, one or more binding groups configured topromote binding with the metal and one or more attachment groupsconfigured to attach to the organic molecule to the surface.

Embodiments of the present invention further provide kits comprising oneor more heat resistance organic molecules derivatized with one or moreattachment groups and instruction materials for carrying out a processof deposing said molecules on a surface or substrate.

BRIEF DESCRIPTION OF THE FIGURES

The foregoing and other aspects of the present invention will beapparent upon consideration of the following detailed description, takenin conjunction with the accompanying drawings, in which like referencecharacters refer to like parts throughout, and in which:

FIG. 1 shows an exemplary reaction scheme for reaction of a surfaceaccording to one embodiment of the method of the present invention;

FIG. 2 illustrates a simplified schematic diagram of a device showingvarious components according to one embodiment of the present invention;

FIG. 3 shows a simplified exemplary reaction scheme for attachingorganic molecules or films to the surface of a substrate, such as butnot limited to an epoxy PCB substrate, according to one embodiment ofthe present invention;

FIG. 4 illustrates exemplary embodiments of organic molecules suitableas a seed layer with various X and Y groups for attachment to copper andcarbon substrates, respectively, according to embodiments of the presentinvention;

FIG. 5 illustrates an exemplary reaction method for attaching organicmolecules to standard, or unmodified, epoxy substrates according to somemethods of the present invention;

FIG. 6 depicts an exemplary reaction method for attaching organicmolecules to desmeared epoxy substrates (e.g., typically having apartially roughened or oxidized surface), according to some methods ofthe present invention;

FIG. 7 shows an exemplary reaction method for attaching organicmolecules to partially cured epoxy substrates (e.g., residual epoxides)according to some methods of the present invention;

FIG. 8A and FIG. 8B illustrate possible reaction mechanisms by whichcopper is formed on the organic molecule seed layer according to somemethods of the present invention;

FIG. 9 illustrates experimental process flow diagrams comprisingmolecule attachment, electroless Cu deposition, electrolytic Cudeposition, and heat treatment;

FIG. 10 and FIG. 11 depict molecule surface coverage on an epoxy surfacequantified by UV absorption as a function of solution concentration andattachment temperature, respectively;

FIGS. 12A and 12B schematically illustrates the qualitativecharacterization of peel strength of electroless copper deposited onepoxy substrate according to methods of the present invention;

FIG. 13 and FIG. 14 are photographs of test coupons showing the impactof porphyrin molecules on the adhesion of electroless copper on epoxysurfaces formed according to methods of the present invention asrepresented by tape peeling tests, and compared to control test coupons;

FIGS. 15A and 15B show magnified photographs of substrates demonstratingthe impact of porphyrin molecules on the defect density of electrolesscopper according to methods of the present invention as observed withoptical spectroscopy;

FIGS. 16A and 16B schematically illustrates quantitativecharacterization of peel strength of electrolytic copper deposited onepoxy substrate according to methods of the present invention; and

FIG. 17 graphically depicts peel strength as a function of time forsubstrates prepared according to embodiments of the present inventionand compared to that prepared conventionally, and demonstrates theenhancement of peel strength of electrolytic Cu by porphyrin moleculesformed on surfaces according to methods of the present invention.

DESCRIPTION OF THE INVENTION

It is to be understood that both the foregoing general description andthe following description are exemplary and explanatory only and are notrestrictive of the methods and devices described herein. In thisapplication, the use of the singular includes the plural unlessspecifically state otherwise. Also, the use of “or” means “and/or”unless state otherwise. Similarly, “comprise,” “comprises,”“comprising,” “include,” “includes” “including” “has” and “having” arenot intended to be limiting.

The present invention provides a process for attaching and growing afilm of an organic molecular layer on(to) a variety of surfaces, whichconstitutes a solution to the above mentioned problems of the prior art.This film has the property that it stabilizes the deposition of elementsused for electroplating (e.g., Cu, Ni, Pd) and provides a more suitablesubstrate for electroplating than the original surface.

In some embodiments, methods of the present invention are performed bythermally-induced reaction of at least one thermally-stable molecularspecies that is a precursor of the said organic film, comprising thesteps of attaching and growing the film by contacting the molecularspecies with a surface, either in solution or via chemical vapordeposition, heating the surface to induce a chemical reaction whichbinds the molecule to the surface, then washing off the excess throughaddition and removal of a solvent which can dissolve the unreactedmolecules. This is followed by electroplating the desired metalutilizing conventional procedures. The attached molecule stabilizes themetal ion on the surface and promotes electroplating.

In one embodiment, the invention provides methods for attachingmolecular species to electronic material surfaces. In some embodimentsthe molecules include porphyrins and related species. The electronicmaterials include but are not limited to: silicon, silicon oxide,silicon nitride, metals, metal oxides, metal nitrides and printedcircuit board substrates, including carbon-based materials such aspolymers and epoxies. The attachment procedure is simple, can becompleted in short times, requires minimal amounts of material, iscompatible with diverse molecular functional groups, and in someinstances affords unprecedented attachment motifs. These featuresgreatly enhance the integration of the molecular materials into theprocessing steps that are needed to complete the plating process.

In one embodiment, this invention provides a method of coupling anorganic molecule to a surface of a Group II, III, IV, V, or VI elementor to a semiconductor comprising a Group II, III, IV, V, or VI element(more preferably to a material comprising a Group III, IV, or V element)or to a transition metal, transition metal oxide or nitride and/or to analloy comprising a transition metal or to another metal.

In certain embodiments, as illustrated generally in FIG. 1, the presentinvention provides methods of coupling a molecule to a surface where themethod includes providing one or more heat-resistant organic moleculesbearing an attachment group; heating the molecule(s) or mixture ofdifferent molecules and/or the surface to a temperature of at leastabout 50° C.; and contacting the molecule(s) to the surface whereby themolecule(s) form a linkage to the surface. In certain embodiments, theorganic molecule(s) are electrically coupled to the surface. In otherembodiments the molecules are covalently linked to the surface. Themethod can, optionally, be performed under an inert atmosphere (e.g. Ar,N₂). In certain embodiments, the heating comprises heating themolecule(s) to a gas phase and the contacting comprises contacting thegas phase to the surface. In certain embodiments, the heating comprisesheating the molecule(s) and/or the surface while the molecule is incontact with the surface. In certain embodiments, the heating comprisesapplying the molecule(s) to the surface and then simultaneously orsubsequently heating the molecule(s) and/or surface. The organicmolecule(s) can be provided in a solvent or dry, or in gas phase, orotherwise not in a solvent. The molecule(s) can be placed into contactwith the surface by dipping in a solution of the molecule, spraying asolution of the molecule, ink-jet printing, or vapor deposition of themolecule directly onto the surface, and the like. Of one particularadvantage, the method of the present invention is suited for coatingnon-planar substrates and surfaces. For example, the organic molecules(s) may be attached to curved or other non-planar surfaces andsubstrates.

In certain embodiments, the heating is to a temperature of at leastabout 25° C., preferably at least about 50° C., more preferably at leastabout 100° C., and most preferably at least about 150° C. Heating can beaccomplished by any convenient method, e.g. in an oven, on a hot plate,in a CVD device, in an MBE device, and the like. In some embodiments thesurface comprises PCB substrates such as polymer and carbon materials,including but not limited to epoxy, glass reinforced epoxy, phenol,polyimide resins glass reinforced polyimide, cyanate, esters, Teflon,and the like. In other embodiments, the surface comprises a materialselected from the group consisting of a Group III element, a Group IVelement, a Group V element, a semiconductor comprising a Group IIIelement, a semiconductor comprising a Group IV element, a semiconductorcomprising a Group V element, a transition metal, and a transition metaloxide. Certain preferred surfaces comprise one or more of the following:Ga, Au, Ag, Cu, Al, Ta, Ti, Ru, Ir, Pt, Pd, Os, Mn, Hf, Zr, V, Nb, La,Y, Gd, Sr, Ba, Cs, Cr, Co, Ni, Zn, Ga, In, Cd, Rh, Re, W, Mo, andoxides, alloys, mixtures, and/or nitrides thereof. In certainembodiments, the surface comprises a Group III, IV, or V, and/or a dopedGroup III, IV, or V element, e.g. silicon, germanium, doped silicon,doped germanium, and the like. The surface can, optionally, be ahydrogen passivated surface.

In general, in some embodiments the organic molecule is comprised of athermally stable unit or base with one more binding groups X and one ormore attachment groups Y. In certain embodiments, the organic moleculeis heat-resistant metal-binding molecule, and may be comprised of one ormore “surface active moieties,” also referred to in associatedapplications as “redox active moieties” or “ReAMs”. One embodiment ofthe invention encompasses the use of compositions of molecularcomponents using surface active moieties generally described in U.S.Pat. Nos. 6,208,553, 6,381,169, 6,657,884, 6,324,091, 6,272,038,6,212,093, 6,451,942, 6,777,516, 6,674,121, 6,642,376, 6,728,129, USPublication Nos: 20070108438, 20060092687, 20050243597, 2006020958720060195296 20060092687 20060081950 20050270820 20050243597 2005020720820050185447 20050162895 20050062097 20050041494 20030169618 2003011167020030081463 20020180446 20020154535 20020076714, 2002/0180446,2003/0082444, 2003/0081463, 2004/0115524, 2004/0150465, 2004/0120180,2002/010589, U.S. Ser. Nos. 10/766,304, 10/834,630, 10/628,868,10/456,321, 10/723,315, 10/800,147, 10/795,904, 10/754,257, 60/687,464,all of which are expressly incorporated in their entirety. Note thatwhile in the associated applications listed immediately above, theheat-resistant molecule is sometime referred to as “redox activemoieties” or “ReAMs,” in the instant application term surface activemoiety is more appropriate. In general, in some embodiments there areseveral types of surface active moieties useful in the presentinvention, all based on polydentate proligands, including macrocyclicand non-macrocyclic moieties. A number of suitable proligands andcomplexes, as well as suitable substituents, are outlined in thereferences cited above. In addition, many polydentate proligands caninclude substitution groups (often referred to as “R” groups herein andwithin the cited references, and include moieties and definitionsoutlined in U.S. Pub. No. 2007/0108438, incorporated by reference hereinspecifically for the definition of the substituent groups.

Suitable proligands fall into, two categories: ligands which usenitrogen, oxygen, sulfur, carbon or phosphorus atoms (depending on themetal ion) as the coordination atoms (generally referred to in theliterature as sigma (a) donors) and organometallic ligands such asmetallocene ligands (generally referred to in the literature as pidonors, and depicted in U.S. Pub. No. 2007/0108438 as Lm).

In addition, a single surface active moiety may have two or more redoxactive subunits, for example, as shown in FIG. 13A of U.S. Pub. No.2007/0108438, which utilizes porphyrins and ferrocenes.

In some embodiments, the surface active moiety is a macrocyclic ligand,which includes both macrocyclic proligands and macrocyclic complexes. By“macrocyclic proligand” herein is meant a cyclic compound which containdonor atoms (sometimes referred to herein as “coordination atoms”)oriented so that they can bind to a metal ion and which are large enoughto encircle the metal atom. In general, the donor atoms are heteroatomsincluding, but not limited to, nitrogen, oxygen and sulfur, with theformer being especially preferred. However, as will be appreciated bythose in the art, different metal ions bind preferentially to differentheteroatoms, and thus the heteroatoms used can depend on the desiredmetal ion. In addition, in some embodiments, a single macrocycle cancontain heteroatoms of different types.

A “macrocyclic complex” is a macrocyclic proligand with at least onemetal ion; in some embodiments the macrocyclic complex comprises asingle metal ion, although as described below, polynucleate complexes,including polynucleate macrocyclic complexes, are also contemplated.

A wide variety of macrocyclic ligands find use in the present invention,including those that are electronically conjugated and those that maynot be. A broad schematic of a suitable macrocyclic ligand is shown anddescribed in FIG. 15 of U.S. Pub. No. 2007/0108438. In some embodiments,the rings, bonds and substitutents are chosen to result in the compoundbeing electronically conjugated, and at a minimum to have at least twooxidation states.

In some embodiments, the macrocyclic ligands of the invention areselected from the group consisting of porphyrins (particularly porphyrinderivatives as defined below), and cyclen derivatives. A particularlypreferred subset of macrocycles suitable in the invention areporphyrins, including porphyrin derivatives. Such derivatives includeporphyrins with extra rings ortho-fused, or ortho-perifused, to theporphyrin nucleus, porphyrins having a replacement of one or more carbonatoms of the porphyrin ring by an atom of another element (skeletalreplacement), derivatives having a replacement of a nitrogen atom of theporphyrin ring by an atom of another element (skeletal replacement ofnitrogen), derivatives having substituents other than hydrogen locatedat the peripheral (meso-, (3- or core atoms of the porphyrin,derivatives with saturation of one or more bonds of the porphyrin(hydroporphyrins, e.g., chlorins, bacteriochlorins, isobacteriochlorins,decahydroporphyrins, corphins, pyrrocorphins, etc.), derivatives havingone or more atoms, including pyrrolic and pyrromethenyl units, insertedin the porphyrin ring (expanded porphyrins), derivatives having one ormore groups removed from the porphyrin ring (contracted porphyrins,e.g., corrin, corrole) and combinations of the foregoing derivatives(e.g. phthalocyanines, sub-phthalocyanines, and porphyrin isomers).Additional suitable porphyrin derivatives include, but are not limitedto the chlorophyll group, including etiophyllin, pyrroporphyrin,rhodoporphyrin, phylloporphyrin, phylloerythrin, chlorophyll a and b, aswell as the hemoglobin group, including deuteroporphyrin, deuterohemin,hemin, hematin, protoporphyrin, mesohemin, hematoporphyrinmesoporphyrin, coproporphyrin, uruporphyrin and turacin, and the seriesof tetraarylazadipyrromethines.

As will be appreciated by those in the art, each unsaturated position,whether carbon or heteroatom, can include one or more substitutiongroups as defined herein, depending on the desired valency of thesystem.

In addition, included within the definition of “porphyrin” are porphyrincomplexes, which comprise the porphyrin proligand and at least one metalion. Suitable metals for the porphyrin compounds will depend on theheteroatoms used as coordination atoms, but in general are selected fromtransition metal ions. The term “transition metals” as used hereintypically refers to the 38 elements in groups 3 through 12 of theperiodic table. Typically transition metals are characterized by thefact that their valence electrons, or the electrons they use to combinewith other elements, are present in more than one shell and consequentlyoften exhibit several common oxidation states. In certain embodiments,the transition metals of this invention include, but are not limited toone or more of scandium, titanium, vanadium, chromium, manganese, iron,cobalt, nickel, copper, zinc, yttrium, zirconium, niobium, molybdenum,technetium, ruthenium, rhodium, palladium, silver, cadmium, hafnium,tantalum, tungsten, rhenium, osmium, iridium, platinum, palladium, gold,mercury, rutherfordium, and/or oxides, and/or nitrides, and/or alloys,and/or mixtures thereof.

There are also a number of macrocycles based on cyclen derivatives. FIG.17 13C of U.S. Pub. No. 2007/0108438, depicts a number of macrocyclicproligands loosely based on cyclen/cyclam derivatives, which can includeskeletal expansion by the inclusion of independently selected carbons orheteroatoms. In some embodiments, at least one R group is a surfaceactive subunit, preferably electronically conjugated to the metal. Insome embodiments, including when at least one R group is a surfaceactive subunit, two or more neighboring R2 groups form cyclo or an arylgroup. In the present invention, the at least on R group is a surfaceactive subunit or moiety.

Furthermore, in some embodiments, macrocyclic complexes relyingorganometallic ligands are used. In addition to purely organic compoundsfor use as surface active moieties, and various transition metalcoordination complexes with 8-bonded organic ligand with donor atoms asheterocyclic or exocyclic substituents, there is available a widevariety of transition metal organometallic compounds with pi-bondedorganic ligands (see Advanced Inorganic Chemistry, 5th Ed., Cotton &Wilkinson, John Wiley & Sons, 1988, chapter 26; Organometallics, AConcise Introduction, Elschenbroich et al., 2nd Ed., 1992, 30 VCH; andComprehensive Organometallic Chemistry II, A Review of the Literature1982-1994, Abel et al. Ed., Vol. 7, chapters 7, 8, 1.0 & 11, PergamonPress, hereby expressly incorporated by reference). Such organometallicligands include cyclic aromatic compounds such as the cyclopentadienideion [C₅H₅(−1)] and various ring substituted and ring fused derivatives,such as the indenylide (−1) ion, that yield a class ofbis(cyclopentadienyl)metal compounds, (i.e. the metallocenes); see forexample Robins et al., J. Am. Chem. Soc. 104:1882-1893 (1982); andGassman et al., J. Am. Chem. Soc. 108:4228-4229 (1986), incorporated byreference. Of these, ferrocene [(C₅H₅)₂Fe] and its derivatives areprototypical examples which have been used in a wide variety of chemical(Connelly et al., Chem. Rev. 96:877-910 (1996), incorporated byreference) and electrochemical (Geiger et al., Advances inOrganometallic Chemistry 23:1-93; and Geiger et al., Advances inOrganometallic Chemistry 24:87, incorporated by reference) reactions.Other potentially suitable organometallic ligands include cyclic arenessuch as benzene, to yield bis(arene)metal compounds and their ringsubstituted and ring fused derivatives, of which bis(benzene)chromium isa prototypical example, Other acyclic n-bonded ligands such as theallyl(−1) ion, or butadiene yield potentially suitable organometalliccompounds, and all such ligands, in conjunction with other 7c-bonded and8-bonded ligands constitute the general class of organometalliccompounds in which there is a metal to carbon bond. Electrochemicalstudies of various dimers and oligomers of such compounds with bridgingorganic ligands, and additional non-bridging ligands, as well as withand without metal-metal bonds are all useful.

In some embodiments, the surface active moieties are sandwichcoordination complexes. The terms “sandwich coordination compound” or“sandwich coordination complex” refer to a compound of the formulaL-Mn-L, where each L is a heterocyclic ligand (as described below), eachM is a metal, n is 2 or more, most preferably 2 or 3, and each metal ispositioned between a pair of ligands and bonded to one or more heteroatom (and typically a plurality of hetero atoms, e.g., 2, 3, 4, 5) ineach ligand (depending upon the oxidation state of the metal). Thussandwich coordination compounds are not organometallic compounds such asferrocene, in which the metal is bonded to carbon atoms. The ligands inthe sandwich coordination compound are generally arranged in a stackedorientation (i.e., are generally cofacially oriented and axially alignedwith one another, although they may or may not be rotated about thataxis with respect to one another) (see, e.g., Ng and Jiang (1997)Chemical Society Reviews 26: 433-442) incorporated by reference.Sandwich coordination complexes include, but are not limited to“double-decker sandwich coordination compound” and “triple-deckersandwich coordination compounds”. The synthesis and use of sandwichcoordination compounds is described in detail in U.S. Pat. Nos.6,212,093; 6,451,942; 6,777,516; and polymerization of these moleculesis described in WO 2005/086826, all of which are included herein,particularly the individual substitutent groups that find use in bothsandwich complexes and the “single macrocycle” complexes.

In addition, polymers of these sandwich compounds are also of use; thisincludes “dyads” and “triads” as described in U.S. Pat. Nos. 6,212,093;6,451,942; 6,777,516; and polymerization of these molecules as describedin WO 2005/086826, all of which are incorporated by reference andincluded herein.

Surface active moieties comprising non-macrocyclic chelators are boundto metal ions to form non-macrocyclic chelate compounds, since thepresence of the metal allows for multiple proligands to bind together togive multiple oxidation states.

In some embodiments, nitrogen donating proligands are used. Suitablenitrogen donating proligands are well known in the art and include, butare not limited to, NH2; NFIR; NRR′; pyridine; pyrazine;isonicotinamide; imidazole; bipyridine and substituted derivatives ofbipyridine; terpyridine and substituted derivatives; phenanthrolines,particularly 1,10-phenanthroline (abbreviated phen) and substitutedderivatives of phenanthrolines such as 4,7-dimethylphenanthroline anddipyridol[3,2-a:2′,3′-c]phenazine (abbreviated dppz); dipyridophenazine;1,4,5,8,9,12-hexaazatriphenylene (abbreviated hat);9,10-phenanthrenequinone diimine (abbreviated phi);1,4,5,8-tetraazaphenanthrene (abbreviated tap);1,4,8,11-tetra-azacyclotetradecane (abbreviated cyclam) and isocyanide.Substituted derivatives, including fused derivatives, may also be used.It should be noted that macrocylic ligands that do not coordinativelysaturate the metal ion, and which require the addition of anotherproligand, are considered non-macrocyclic for this purpose. As will beappreciated by those in the art, it is possible to covalent attach anumber of “non-macrocyclic” ligands to form a coordinatively saturatedcompound, but that is lacking a cyclic skeleton.

Suitable sigma donating ligands using carbon, oxygen, sulfur andphosphorus are known in the art. For example, suitable sigma carbondonors are found in Cotton and Wilkenson, Advanced Organic Chemistry,5th Edition, John Wiley & Sons, 1988, hereby incorporated by reference;see page 38, for example. Similarly, suitable oxygen ligands includecrown ethers, water and others known in the art. Phosphines andsubstituted phosphines are also suitable; see page 38 of Cotton andWilkenson.

The oxygen, sulfur, phosphorus and nitrogen-donating ligands areattached in such a manner as to allow the heteroatoms to serve ascoordination atoms.

In addition, some embodiments utilize polydentate ligands that arepolynucleating ligands, e.g. they are capable of binding more than onemetal ion. These may be macrocyclic or non-macrocyclic.

The molecular elements herein may also comprise polymers of the surfaceactive moieties as outlined above; for example, porphyrin polymers(including polymers of porphyrin complexes), macrocycle complexpolymers, Surface active moieties comprising two surface activesubunits, etc. can be utilized. The polymers can be homopolymers orheteropolymers, and can include any number of different mixtures(admixtures) of monomeric surface active moiety, wherein “monomer” canalso include surface active moieties comprising two or more subunits(e.g. a sandwich coordination compound, a porphyrin derivativesubstituted with one or more ferrocenes, etc.). Surface active moietypolymers are described in WO 2005/086826, which is expresslyincorporated by reference in its entirety.

In certain embodiments, the attachment group(s) Y of the surface activemoiety comprises an aryl functional group and/or an alkyl attachmentgroup. In certain embodiments, the aryl functional group comprises afunctional group selected from the group consisting of amino,alkylamino, bromo, iodo, hydroxy, hydroxymethyl, formyl, bromomethyl,vinyl, allyl, S-acetylthiomethyl, Se-acetylselenomethyl, ethynyl,2-(trimethylsilyl)ethynyl, mercapto, mercaptomethyl,4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl, and dihydroxyphosphoryl. Incertain embodiments, the alkyl attachment group comprises a functionalgroup selected from the group consisting of bromo, iodo, hydroxy,formyl, vinyl, mercapto, selenyl, S-acetylthio, Se-acetylseleno,ethynyl, 2-(trimethylsilyl)ethynyl,4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl, and dihydroxyphosphoryl. Incertain embodiments, the attachment group comprises an alcohol or aphosphonate.

In certain embodiments, the contacting comprises selectively contactingthe organic molecule to certain regions of the surface and not to otherregions. For example, the contacting comprises placing a protectivecoating (e.g. a masking material) on the surface in regions where theorganic molecule(s) are not to be attached; contacting the molecule(s)with the surface; and removing the protective coating to provide regionsof the surface without the organic molecule(s). In certain embodiments,the contacting comprises contact printing of a solution comprising theorganic molecule(s) or the dry organic molecule(s) onto the surface. Incertain embodiments, the contacting comprises spraying or dropping asolution comprising the organic molecule(s) or applying the dry organicmolecule(s) onto the surface. In certain embodiments, the contactingcomprises contacting the surface with the molecule(s) and subsequentlyetching selected regions of the surface to remove the organicmolecule(s). In certain embodiments, the contacting comprises molecularbeam epitaxy (MBE), and/or chemical vapor deposition (CVD), atomic layerdeposition (ALD), molecular layer deposition (MLD) and/orplasma-assisted vapor deposition, and/or sputtering and the like. Incertain embodiments, the heat-resistant organic molecule comprises amixture at least two different species of heat-resistant organicmolecule and the heating comprises heating the mixture and/or thesurface.

This invention also provides a method of coupling a metal-bindingmolecule (or a collection of different species of metal-bindingmolecules) to a surface. In some embodiments the method comprisesheating the molecule(s) to a gas phase; and contacting the molecule(s)to a surface whereby the metal-binding molecule(s) couple to thesurface. In certain embodiments, the metal-binding molecule ischemically coupled to the surface and/or electrically coupled to thesurface. In certain embodiments, the heating is to a temperature of atleast about 25° C., preferably at least about 50° C., more preferably atleast about 100° C., and most preferably at least about 150° C. Heatingcan be accomplished by any convenient method, e.g. in an oven, on a hotplate, in a CVD device, in an MBE device, and the like.

In certain embodiments, the surface is comprised a material selectedfrom the group of a Group III element, a Group IV element, a Group Velement, a semiconductor comprising a Group III element, a semiconductorcomprising a Group IV element, a semiconductor comprising a Group Velement, a transition metal, a transition metal oxide, a plasticmaterial, epoxy, ceramic, carbon and the like as described above. Incertain embodiments, the surface comprises a material such as Au, Ag,Cu, Al, Ta, Ti, Ru, Ir, Pt, Pd, Os, Mn, Hf, Zr, V, Nb, La, Y, Gd, Sr,Ba, Cs, Cr, Co, Ni, Zn, Ga, In, Cd, Rh, Re, W, Mo, and/or oxides,nitrides, mixtures, or alloys thereof. In certain embodiments, themetal-binding molecule includes, but is not limited to any of themolecules described herein. Similarly the attachment groups include, butare not limited to any of the attachment groups described herein. Incertain embodiments, the Group II, III, IV, V, or VI element, morepreferably a Group III, IV, or V, element, still more preferably a GroupIV element or a doped Group IV element (e.g., silicon, germanium, dopedsilicon, doped germanium, etc.). In certain embodiments, the contactingcomprises selectively contacting the volatilized organic molecule tocertain regions of the surface and not to other regions. In certainembodiments, the contacting comprises: placing a protective coating onthe surface in regions where the metal-binding molecule is not to beattached; contacting the molecule with the surface; and removing theprotective coating to provide regions of the surface without themetal-binding molecule. In certain embodiments, the contacting comprisescontacting the surface with the molecule and subsequently etchingselected regions of the surface to remove the metal-binding molecule. Incertain embodiments, the contacting comprises molecular beam epitaxy(MBE), and/or chemical vapor deposition (CVD), and/or plasma-assistedvapor deposition, and/or sputtering, and the like.

In another embodiment, this invention provides a surface of a Group II,III, IV, V, or VI element or a surface of a semiconductor comprising aGroup II, III, IV, V, or VI or a transition metal, transition metaloxide, or nitride, or alloy, or mixture having an organic moleculecoupled thereto, where the organic molecule is coupled to said surfaceby methods described herein. In certain embodiments, the organicmolecule is a metal-binding molecule and includes, but is not limited toany of the molecules described herein. Similarly the attachment groupsinclude, but are not limited to any of the attachment groups describedherein. In certain embodiments, the Group II, III, IV, V, or VI element,more preferably a Group III, IV, or V, element, still more preferably aGroup IV element or a doped Group IV element (e.g., silicon, germanium,doped silicon, doped germanium, etc.).

In another embodiment, this invention provides a method of fabricatingan ordered molecular assembly for use in metal plating as illustrated inFIG. 2. In particular, FIG. 2 illustrates a simplified schematic of adouble sided device 100 having two epoxy substrates 102 and 104. In theexemplary embodiment, a layer of organic molecules 106 and 108 arecoupled to the surface of each epoxy substrate 102 and 104 and form aninterface for copper plating or binding. A copper seed layer 110 isformed on one of the layers of organic molecules. Formed atop the copperseed layer 110 is a electroless plated copper 112, followed by bulkcopper 114 typically formed by electroplating. The copper layers aresandwiched between the two epoxy substrates. While one particulararrangement is shown in FIG. 2, many other devices with differentarrangement of layers, single sided devices, devices with vias, and thelike, are all within the spirit and scope of the invention. In someembodiments, the method generally involves providing a heat-resistantorganic molecule (or a plurality of different heat resistant organicmolecules) derivatized with an attachment group; heating the moleculeand/or a surface to a temperature of at least about 100° C.; where thesurface comprises a PCB substrates such as polymer and other organicmaterials, including but not limited to epoxy, glass reinforced epoxy,phenol, polyimide resins glass reinforced polyimide, cyanate, esters,Teflon, or a Group III, IV, or V element or a transition metal or metaloxide; contacting the molecule(s) at a plurality of discrete locationson the surface whereby the attachment groups form bonds (such as but notlimited to covalent or ionic bonds) with the surface at the plurality ofdiscrete locations. In certain embodiments, the heating is to atemperature of at least about 25° C. but below the decompositiontemperature of the system components, preferably at least about 50° C.,more preferably at least about 100° C., and most preferably at leastabout 150° C. In certain embodiments, the organic molecule is ametal-binding molecule and includes, but is not limited to any of themolecules described herein. Similarly the attachment groups include, butare not limited to any of the attachment groups described herein.

This invention also provide kits for coupling an organic molecule to thesurface of a type III, IV, or V material or a transition metal ortransition metal oxide. The kits typically include a containercontaining a heat-resistant organic molecule derivatized with anattachment group (e.g., as described herein) and, optionally,instructional materials teaching coupling the organic molecule to thesurface by heating the molecule and/or the surface to a temperature ofabout 100° C. or more.

The methods of the present invention are suited to treatingnon-conductive surfaces (such as epoxy, glass, SiO₂, SiN, etc) as wellas conductive surfaces, such as copper, gold, platinum, etc., and to“non-noble” surfaces, such as surfaces containing reducible oxide, agraphite surface, a conductive or semiconductive organic surface, asurface of an alloy, a surface of one (or more) conventional conductivepolymer(s), such as a surface based on pyrrole, on aniline, onthiophene, on EDOT, on acetylene or on polyaromatics, etc., a surface ofan intrinsic or doped semiconductor, and any combination of thesecompounds.

Mixtures of these various molecular compounds may also be used accordingto the present invention.

In addition, methods of the present invention make it possible tomanufacture organic films that can simultaneously provide protectionagainst the external medium, for example against corrosion, and/or offeran attached coating that has organic functional groups such as thosementioned above and/or promote or maintain electrical conductivity atthe surface of the treated objects.

It is thus also possible, by methods of the present invention, tomanufacture multilayer conductive structures, for example by usingorganic intercalating films based on the present invention.

In some embodiments, the organic films obtained according to the presentinvention constitute an attached protective coating, which withstandsanodic potentials above the corrosion potential of the conductivesurface to which they have been attached.

Methods of the present invention may thus also comprise, for example, astep of depositing a film of a vinyl polymer by thermal polymerizationof the corresponding vinyl monomer on the conductive polymer film.

Methods of the present invention may also be used to produce very strongorganic/conductor interfaces. Specifically, the organic films of thepresent invention are conductive at any thickness. When they aresparingly crosslinked, they can constitute “conductive sponges”, with aconductive surface whose apparent area is very much greater than theoriginal surface onto which they are attached. This makes it possible toproduce a much more dense functionalization than on the starting surfaceonto which they are attached.

The present invention consequently makes it possible to produce attachedand conductive organic coatings, of adjustable thickness, on conductiveor semiconductive surfaces.

Methods of the present invention can be used, for example, to protectnon-noble metals against external attack, such as those produced bychemical agents, such as corrosion, etc. This novel protection impartedby means of the invention can, for example, prove to be particularlyadvantageous in connections or contacts, where the electrical conductionproperties are improved and/or conserved.

In another application, methods of the present invention can be used,for example, for the manufacture of covering attached sublayers, on alltypes of conductive or semiconductive surfaces, on which all types offunctionalizations may be performed, and especially those usingelectrochemistry, for instance the electro-deposition orelectro-attaching of vinyl monomers, of strained rings, of diazoniumsalts, of carboxylic acid salts, of alkynes, of Grignard derivatives,etc. This sublayer can thus constitute a high-quality finishing for theremetallization of objects, or to attach functional groups, for examplein the fields of biomedics, biotechnology, chemical sensors,instrumentation, etc.

The present invention may thus be used, for example, in the manufactureof an encapsulating coating for electronic components, in themanufacture of a hydrophilic coating, in the manufacture of abiocompatible coating, for the manufacture of a film that can be used asan adhesion primer, as an organic post-functionalization support, as acoating with optical absorption properties or as a coating with stealthproperties.

Of particular advantage the present invention may be used to provide amolecular adhesion layer for electroless deposition and/orelectroplating of metals. In one instance, molecules are attached toprinted circuit board substrates, such as polymer, epoxy or carboncoated substrates to provide a seed layer for electroless plating of ametal, such as electroless copper plating. According to teaching of thepresent invention, such molecules exhibit a strong bond to the organicsubstrate, and/or a strong organic-Cu bond. In some embodiments themolecules exhibit a covalent bond. The high affinity of the attachedmolecule facilitates electroless plating of the copper, which is thenused as a seed layer to electroplate larger quantities of copper.Adhesion layers can be used on a wide number of substrates for a varietyof purposes, such as silicon substrates used in solar energy devices toallow electroplating of a metal layer; through-hole vias on asemiconductor device to allow metal connection(s) between adjacentsurfaces and devices; the backside of semiconductor parts, to allowdeposition of metal layers, which can subsequently be used to formcapacitors; packaging substrates, to allow deposition of metal layersfor patterning and interconnects; as well as many types of flexibleorganic substrates to allow the deposition of metal layers.

According to some embodiments, after formation of defined structures onthe substrate, electroless plating is used to form a first metalliccoating over the substrate surfaces and electrolytic copper depositionis then used to enhance the thickness of the coating. Alternatively,electrolytic copper may be plated directly over a suitably preparedmicrovia as disclosed in any of U.S. Pat. Nos. 5,425,873; 5,207,888; and4,919,768. The next step in the process comprises electroplating copperonto the thus prepared conductive microvias using an electroplatingsolution of the invention. A wide variety of substrates may be platedwith the compositions of the invention, as discussed above. Thecompositions of the invention are particularly useful to plate difficultwork pieces, such as circuit board substrates with small diameter, highaspect ratio microvias and other apertures. The plating compositions ofthe invention also will be particularly useful for plating integratedcircuit devices, such as formed semiconductor devices and the like.

For example in some embodiments, as illustrated in FIG. 3 and FIG. 4,the molecules will comprise binding group(s) X which promote favorableorganic-Cu bonds. Examples of suitable binding groups X include but arenot limited to thiols, nitriles, thiocyanates, amines, alcohols andethers. The molecules further comprise attachment group(s) Y whichpromote favorable molecule-organic substrate bonds. Examples of suitableY groups include but are not limited to amines, alcohols, ethers, othernucleophile, phenyl ethynes, phenyl allylic groups and the like.According to embodiments of the present invention, and withoutlimitation, some suitable molecules are shown in FIG. 4.

In another embodiment, molecules are attached to a metal or metalnitride present on a surface or substrate (e.g., Ta or TaN) to provide aseed layer for copper electroplating. In this embodiment molecules areprovided that have attachment groups Y with a strong bond to TaN or Ta,and binding groups X that exhibit a strong Cu bond to reduceelectromigration, and that the molecular layer is thin and/orconductive, as high current densities will be conducted from TaN to Cu,through the organic layer. The molecules would also attach to TaO₂,since TaN is likely to have some oxide once exposed to atmosphere.

Significantly, the present invention provides for selection ofparticular binding groups X and attachment groups Y depending upon theapplication. This allows one to practice the invention with a wide rangeof substrate materials, thus providing a flexible, robust process and asignificant advance over conventional techniques. For example, FIG. 5illustrates an exemplary reaction method for attaching organic moleculesto standard epoxy substrates. Further, the methods of the presentinvention may be practiced with substrates which have undergone surfacetreatment. For example, FIG. 6 depicts an exemplary reaction method forattaching organic molecules to epoxy substrates having a partiallyroughened or oxidized surface. FIG. 7 shows an exemplary reaction methodfor attaching organic molecules to partially cured epoxy substrates(residual epoxides).

Electroplating solutions of the invention generally comprise at leastone soluble, copper salt, an electrolyte and a brightener component.More particularly, electroplating compositions of the inventionpreferably contain a copper salt; an electrolyte, preferably an acidicaqueous solution such as a sulfuric acid solution with a chloride orother halide ion source; and one or more brightener agents as discussedabove. Electroplating compositions of the invention also preferablycontain a suppressor agent. The plating compositions also may containother components such as one or more leveler agents and the like.

A variety of copper salts may be employed in the subject electroplatingsolutions, including for example copper sulfates, copper acetates,copper fluoroborate, and cupric nitrates. Copper sulfate pentahydrate isa particularly preferred copper salt. A copper salt may be suitablypresent in a relatively wide concentration range in the electroplatingcompositions of the invention. Preferably, a copper salt will beemployed at a concentration of from about 10 to about 300 grams perliter of plating solution, more preferably at a concentration of fromabout 25 to about 200 grams per liter of plating solution, still morepreferably at a concentration of from about 40 to about 175 grams perliter of plating solution.

Plating baths of the invention preferably employ an acidic electrolyte,which typically will be an acidic aqueous solution and that preferablycontains a halide ion source, particularly a chloride ion source.Examples of suitable acids for the electrolyte include sulfuric acid,acetic acid, fluoroboric acid, methane sulfonic acid and sulfamic acid.Sulfuric acid is generally preferred. Chloride is a generally preferredhalide ion. A wide range of halide ion concentrations (if a halide ionis employed) may be suitably utilized, e.g. from about 0 (where nohalide ion employed) to 100 parts per million (ppm) of halide ion in theplating solution, more preferably from about 25 to about 75 ppm ofhalide ion source in the plating solution.

Embodiments of the invention also include electroplating baths that aresubstantially or completely free of an added acid and may be neutral oressentially neutral (e.g. pH of at least less than about 8 or 8.5). Suchplating compositions are suitably prepared in the same manner with thesame components as other compositions disclosed herein but without anadded acid. Thus, for instance, a preferred substantially neutralplating composition of the invention may have the same components as theplating bath of Example 3 which follows, but without the addition ofsulfuric acid. A wide variety of brighteners, including known brighteneragents, may be employed in the copper electroplating compositions of theinvention. Typical brighteners contain one or more sulfur atoms, andtypically without any nitrogen atoms and a molecular weight of about1000 or less. In addition to the copper salts, electrolyte andbrightener, plating baths of the invention optionally may contain avariety of other components, including organic additives such assuppressors agents, leveling agents and the like. Use of a suppressoragent in combination with an enhanced brightener concentration isparticularly preferred and provides surprisingly enhanced platingperformance, particularly in bottom-fill plating of small diameterand/or high aspect ratio microvias.

Use of one or more leveling agents in plating baths of the invention isgenerally preferred. Examples of suitable leveling agents are describedand set forth in U.S. Pat. Nos. 3,770,598, 4,374,709, 4,376,685,4,555,315 and 4,673,459. In general, useful leveling agents includethose that contain a substituted amino group such as compounds havingR—N—R′, where each R and R′ is independently a substituted orunsubstituted alkyl, group or a substituted or unsubstituted aryl group.Typically the alkyl groups have from 1 to 6 carbon atoms, more typicallyfrom 1 to 4 carbon atoms. Suitable aryl groups include substituted orunsubstituted phenyl or naphthyl. The substituents of the substitutedalkyl and aryl groups may be, for example, alkyl, halo and alkoxy.

Other characteristics and advantages of the present invention will alsobecome apparent to a person skilled in the art on reading the examplesbelow, given as non-limiting illustrations, with reference to theattached figures.

Of particular advantage, various parameters can be optimized forattachment of any particular organic molecule. These include (1) theconcentration of the molecule(s), (2) the baking time, and (3) thebaking temperature. These procedures typically use variousconcentrations of molecules in solution or neat molecules. The use ofvery small amounts of material indicates that relatively small amountsof organic solvents can be used, thereby minimizing environmentalhazards.

In addition, baking times as short as a few minutes (e.g., typicallyfrom about 1 sec to about 1 hr, preferably from about 10 sec to about 30min, more preferably from about 1 minute to about 15, 30, or 45 minutes,and most preferably from about 5 min to about 30 minutes) afford highsurface coverage. Short times minimize the amount of energy that is usedin the processing step.

Baking temperatures as high as 400° C. and greater can be used with nodegradation of certain types of molecules. This result is of importancein that many processing steps in fabricating PCB or semiconductordevices entail high temperature processing. In certain embodiments,preferred baking temperatures range from about 25° C. to about 400° C.,preferably from about 100° C. to about 200° C., more preferably fromabout 150° C. to about 250° C., and most preferably from about 150° C.to about 200° C.

Diverse functional groups on the organic molecules are suitable for usein attachment to silicon or other substrates (e.g. Group III, IV, or Velements, transition metals, transition metal oxides or nitrides,transition metal alloys, etc.). The groups include, but are not limitedto, amine, alcohol, ether, thiol, S-acetylthiol, bromomethyl, allyl,iodoaryl, carboxaldehyde, ethyne, vinyl, hydroxymethyl. It is also notedthat groups such as ethyl, methyl, or arene afford essentially noattachment.

While in certain embodiments, heating is accomplished by placing thesubstrate in an oven, essentially any convenient heating method can beutilized, and appropriate heating and contacting methods can beoptimized for particular (e.g., industrial) production contexts. Thus,for example, in certain embodiments, heating can be accomplished bydipping the surface in a hot solution containing the organic moleculesthat are to be attached. Local heating/patterning can be accomplishedusing for example a hot contact printer, or a laser. Heating can also beaccomplished using forced air, a convection oven, radiant heating, andthe like. The foregoing embodiments are intended to be illustrativerather than limiting.

In some embodiments the organic molecule is provided in a solvent,dispersion, emulsion, paste, gel, or the like. Preferred solvents,pastes, gels, emulsions, dispersions, etc., are solvents that can beapplied to the Group II, III, IV, V, and/or VI material(s), and/ortransition metals without substantially degrading that substrate andthat solubilize or suspend, but do not degrade the organic molecule(s)that are to be coupled to the substrate. In certain embodiments,preferred solvents include high boiling point solvents (e.g., solventswith an initial boiling point greater than about 130° C., preferablygreater than about 150° C., more preferably greater than about 180° C.).Such solvents include, but are not limited to propylene glycolmonomethyl ether acetate (PGMEA), benzonitrile, dimethylformamide,xylene, ortho-dichlorobenzene, and the like.

In some embodiments, to effect attachment to the substrate (e.g., aGroup II, III, IV, V, or VI element, semiconductor, and/or oxide, and/ortransition metal, transition metal oxide or nitride, epoxy or otherpolymer-based material, etc.) the heat-resistant organic molecule eitherbears one or more attachment group(s) Y (e.g., as substituent(s)) and/oris derivatized so that it is attached directly or through a linker tothe substrate.

In certain preferred embodiments, the attachment group Y comprises anaryl or an alkyl group. Certain preferred aryl groups include afunctional group such as amino, alkylamino, bromo, iodo, hydroxy, ether,hydroxymethyl, formyl, bromomethyl, vinyl, allyl, S-acetylthiomethyl,Se-acetylselenomethyl, ethynyl, 2-(trimethylsilyl)ethynyl, mercapto,mercaptomethyl, 4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl, anddihydroxyphosphoryl. Certain preferred alkyls include a functional groupsuch as bromo, iodo, hydroxy, formyl, vinyl, mercapto, selenyl,S-acetylthio, Se-acetylseleno, ethynyl, 2-(trimethylsilyl)ethynyl,4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl, and dihydroxyphosphoryl.

In certain embodiments the attachment groups Y include, but are notlimited to alcohols, thiols, S-acetylthiols, bromomethyls, allyls,iodoaryls, carboxaldehydes, ethynes, and the like. In certainembodiments, the attachment groups include, but are not limited to4-(hydroxymethyl)phenyl, 4-(S-acetylthiomethyl)phenyl,4-(Se-acetylselenomethyl)phenyl, 4-(mercaptomethyl)phenyl,4-(hydroselenomethyl)phenyl, 4-formylphenyl, 4-(bromomethyl)phenyl,4-vinylphenyl, 4-ethynylphenyl, 4-allylphenyl,4-[2-(trimethylsilyl)ethynyl]phenyl,4-[2-(triisopropylsilyl)ethynyl]phenyl, 4-bromophenyl, 4-iodophenyl,4-hydroxyphenyl, 4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)phenylbromo, iodo, hydroxymethyl, S-acetylthiomethyl, Se-acetylselenomethyl,mercaptomethyl, hydroselenomethyl, formyl, bromomethyl, chloromethyl,ethynyl, vinyl, allyl, 4-[2-(4-(hydroxymethyl)-phenyl)ethynyl]phenyl,4-(ethynyl)biphen-4′-yl, 4-[2-(triisopropylsilyl)et-hynyl]biphen-4′-yl,3,5-diethynylphenyl, 2-bromoethyl, and the like. These attachment groupsY are meant to be illustrative and not limiting.

The suitability of other attachment groups Y can readily be evaluated. Aheat-resistant organic molecule bearing the attachment group(s) ofinterest (directly or on a linker) is coupled to a substrate (e.g.,epoxy) according to the methods described herein. The efficacy ofattachment can then be evaluated spectroscopically, e.g., usingreflectance UV absorption measurements.

The attachment groups Y can be substituent(s) comprising theheat-resistant organic molecule. Alternatively, the organic molecule canbe derivatized to link the attachment group(s) Y thereto either directlyor through a linker.

Means of derivatizing molecules, e.g., with alcohols or thiols are wellknown to those of skill in the art (see, e.g., Gryko et al. (1999) J.Org. Chem., 64: 8635-8647; Smith and March (2001) March's AdvancedOrganic Chemistry, John Wiley & Sons, 5th Edition, etc.).

Where the attachment group Y comprises an amine, in certain embodiments,suitable amines include, but are not limited to a primary amine, asecondary amine, a tertiary amine, a benzyl amine, and an aryl amine.Certain particularly preferred amines include, but are not limited to 1to 10 carbon straight chain amine, aniline, and phenethyl amine.

Where the attachment group Y comprises an alcohol, in certainembodiments, suitable alcohols include, but are not limited to a primaryalcohol, a secondary alcohol, a tertiary alcohol, a benzyl alcohol, andan aryl alcohol (i.e., a phenol). Certain particularly preferredalcohols include, but are not limited to 2 to 10 carbon straight chainalcohols, benzyl alcohol, and phenethyl alcohol or ether containing sidegroup.

When the attachment group Y comprises a thiol, in certain embodiments,suitable thiols include, but are not limited to a primary thiol, asecondary thiol, a tertiary thiol, a benzyl thiol, and an aryl thiol.Particularly preferred thiols include, but are not limited to 2 to 10carbon straight chain thiols, benzyl thiol, and phenethyl thiol.

The surface can take essentially any form. For example, it can beprovided as a planar substrate, an etched substrate, a deposited domainon another substrate and the like. Particularly preferred forms includethose forms of common use in solid state electronics and circuit boardfabrication processes. However, the present invention is not limited toconventional substrate shapes. For example, the surface or substrate maybe curves and other non-planar shapes. Additionally, the substrate maybe a photovoltaic or solar cell device.

Although not necessarily required, in certain embodiments the surface iscleaned before and/or after molecule attachment, e.g., using standardmethods known to those of skill in the art. Thus, for example, in onepreferred embodiment, the surface can be cleaned by sonication in aseries of solvents (e.g., acetone, toluene, acetone, ethanol, and water)and then exposed to a standard wafer-cleaning solution (e.g., Piranha(sulfuric acid:30% hydrogen peroxide, 2:1)) at an elevated temperature(e.g., 100° C.). Various alkaline permanganate treatments have been usedas standard methods for desmearing surfaces of printed circuit boards,including the through-holes. Such permanganate treatments have beenemployed for reliably removing wear and drilling debris, as well as fortexturing or micro roughening the exposed epoxy resin surfaces. Thelatter effect significantly improves through-hole metallization byfacilitating adhesion to epoxy resin, at the price of roughening thecopper and decreasing the frequency response of the copper traces. Otherconventional smear removal methods have included treatment with sulfuricacid, chromic acid, and plasma desmear, which is a dry chemical methodin which boards are exposed to oxygen and fluorocarbon gases, e.g. CF4.Generally, permanganate treatments involve three different solutiontreatments used sequentially. They are (1) a solvent swell solution, (2)a permanganate desmear solution, and (3) a neutralization solution. FIG.6 depicts the reaction of molecules with an epoxy substrate that hasbeen desmeared, and has oxidized functional groups available forreaction on the surface.

In certain embodiments, oxides can be removed from the substrate surfaceand the surface can be hydrogen passivated. A number of approaches tohydrogen passivation are well known to those of skill in the art. Forexample, in one approach, a flow of molecular hydrogen is passed throughdense microwave plasma across a magnetic field. The magnetic fieldserves to protect the sample surface from being bombarded by chargedparticles. Hence the crossed beam (CB) method makes it possible to avoidplasma etching and heavy ion bombardment that are so detrimental formany semiconductor devices (see, e.g., Balmashnov, et al. (1990)Semiconductor Science and Technology, 5: 242). In one particularlypreferred embodiment, passivation is by contacting the surface to bepassivated with an ammonium fluoride solution (preferably purged ofoxygen).

Other methods of cleaning and passivating surfaces are known to those ofskill in the art (see, e.g., Choudhury (1997) The Handbook ofMicrolithography, Micromachining, and Microfabrication, Bard & Faulkner(1997) Fundamentals of Electrochemistry, Wiley, New York and the like).

In certain embodiments, the heat-resistant organic molecules areattached to form a uniform or substantially uniform film across thesurface of the substrate. In other embodiments, the organic moleculesare separately coupled at one or more discrete locations on the surface.In certain embodiments, different molecules are coupled at differentlocations on the surface.

The location at which the molecules are coupled can be accomplished byany of a number of means. For example, in certain embodiments, thesolution(s) comprising the organic molecule(s) can be selectivelydeposited at particular locations on the surface. In certain otherembodiments, the solution can be uniformly deposited on the surface andselective domains can be heated. In certain embodiments, the organicmolecules can be coupled to the entire surface and then selectivelyetched away from certain areas. Alternatively, the linker moiety can bedesigned to react selectively with specific functional groups on thesubstrate, allowing the molecule attachment process to act as thepatterning step as well.

The most common approach to selectively contacting the surface with theorganic molecule(s) involves masking the areas of the surface that areto be free of the organic molecules so that the solution or gas phasecomprising the molecule(s) cannot come in contact with the surface inthose areas. This is readily accomplished by coating the substrate witha masking material (e.g., a polymer resist) and selectively etching theresist off of areas that are to be coupled. Alternatively aphotoactivatible resist can be applied to the surface and selectivelyactivated (e.g., via UV light) in areas that are to be protected. Such“photolithographic” methods are well known in the semiconductor industry(see e.g., Van Zant (2000) Microchip Fabrication: A Practical Guide toSemiconductor Processing; Nishi and Doering (2000) Handbook ofSemiconductor Manufacturing Technology; Xiao (2000) Introduction toSemiconductor Manufacturing Technology; Campbell (1996) The Science andEngineering of Microelectronic Fabrication (Oxford Series in ElectricalEngineering), Oxford University Press, and the like). In addition, theresist can be patterned on the surface simply by contact printing theresist onto the surface.

In other approaches, the surface is uniformly contacted with themolecules. The molecules can then be selectively etched off the surfacein areas that are to be molecule free. Etching methods are well known tothose of skill in the art and include, but are not limited to plasmaetching, laser etching, acid etching, and the like.

Other approaches involve contact printing of the reagents, e.g., using acontact print head shaped to selectively deposit the reagent(s) inregions that are to be coupled, use of an inkjet apparatus (see e.g.,U.S. Pat. No. 6,221,653) to selectively deposit reagents in particularareas, use of dams to selectively confine reagents to particularregions, and the like.

In certain preferred embodiments, the coupling reaction is repeatedseveral times. After the reaction(s) are complete, uncoupled organicmolecules are washed off of the surface, e.g., using standard wash steps(e.g., benzonitrile wash followed by sonication in dry methylenechloride). Additional surface cleaning steps (e.g., additional washes,descuming or desmearing steps, and the like) may be used subsequent tomolecule attachment to remove excess unreacted molecules prior to metaldeposition, especially on via containing structures.

In one instance, a molecule consisting of a porphyrin macrocycle with acentral Cu metal was bonded to a TaN surface as described above.Molecules are selected for use based on their affinity to form a bondwith the substrate, their thermal stability and their affinity for Cu²⁺ions. The high affinity of the attached molecule facilitated electrolessplating of the copper, which can then be used as a seed layer toelectroplate larger quantities of copper.

Electroplating on the molecule-covered substrate is accomplished asdescribed above. Briefly, molecule coated substrates are immersed in aplating bath containing appropriate levels of a copper salt, anelectrolyte preferably an acidic aqueous solution such as a sulfuricacid solution with a chloride or other halide ion source, and one ormore brightener agents in enhanced concentrations as discussed above,and preferably a suppressor agent. The plating compositions also maycontain other components such as one or more leveler agents and thelike. A cathodic voltage (e.g., −1 V) is applied to the molecule-coveredsubstrate, causing the reduction of the Cu²⁺ ions to Cu⁰(s), whichdeposit on the molecular layer to form a metallic layer on top of themolecular layer. Without being bound by any particular theory, FIG. 8Aand FIG. 8B illustrate one possible reaction mechanism showing Cu²⁺ iondeposition and subsequent reduction to copper layer Cu⁰(s),respectively. This copper layer has the same properties as a copperlayer that is deposited in conventional protocols, and can be processedsubsequently in similar ways, including lithographic patterning,damascene and dual-damascene processes.

Experimental

The present invention may be better understood from the examples thatfollow. A number of experiments were conducted as described below. Theexamples are shown for illustration purposes only, and are not intendedto limit the invention in any way.

EXAMPLES

In order to further illustrate the features of the present invention, anexemplary experimental process flow schematically illustrated in FIG. 9.comprises four major steps: (1) molecule attachment 200 (2) electrolessCu deposition 300, (3) electrolytic Cu deposition 400, and (4) optionalheat treatment. The specific data and results are shown for illustrativepurposes only and are not intended to limit the scope of the inventionin any way. FIG. 9 shows where in the process the tape peeling and peelstrength tests are carried out, however this is shown only to illustratethe testing procedures. The broad method steps of the present inventiondo not include the peeling test steps. Referring to FIG. 9, in theexemplary experimental procedure, molecular attachment is carried out bycleaning of the substrate 202, depositing or contacting the one or moremolecules with the substrate 204, heating or baking the substrate topromote attachment of the molecules to the substrate at step 206 andthen rinsing the substrate and post treatment 208.

Next electroless deposition of copper is carried out at step 300.Specifically, the substrate may be conditioned 302, rinsed 304 andpre-dipped 306. Activation 308 of the substrate and rinsing 310 againare performed. Acceleration 312 and further rinse step 314 are performedfollowed by electroless copper deposition at step 316. The substratewith electroless copper is then rinsed and dried 318. At this stage, atape peeling test 320 is conducted to determine the quality and adhesionof the copper layer. Actual test results are shown below.

Next electrodeposition of copper is carried out at step 400. Followingthe tape peeling test, the substrate is acid cleaned 402.Electrodeposition of copper on the substrate is then carried out at step404. The substrate is then rinsed and dried 406. Optionally, post heattreatment may be carried out at step 408, followed by peel strengthtesting at step 410. Actual test results are shown below.

Example 1 Molecule Attachment

This example illustrates one exemplary approach to form a layer oforganic molecules on a PCB substrate. In this instance, theethynyl-terminated molecules, shown in FIG. 4, are attached to epoxysurface via the formation of C—C bond, as illustrated in FIG. 5. Acommercial smooth epoxy resin substrate was first cleaned by sonicationfor 5 minutes in water and then isopropyl alcohol. The substrate wascoated with a solution containing 0.1 to 1 mM of the porphyrin moleculein an appropriate solvent (e.g., hexane, toluene, and the like) byeither dip-coating, drop-coating, or spin-coating. The sample was thenbaked at 100 to 200° C. for 20 minutes and followed by standard surfacecleaning processes to remove the residual unattached molecules. Theamount of molecule attached can be adjusted by varying the concentrationof the molecule, the attachment temperature, and duration, and monitoredby UV absorption spectroscopy as illustrated in FIGS. 10 and 11. Asillustrated in FIG. 10, the UV adsorption strength is proportional tothe molecule coverage which increases with increase in attachmentconcentration. Additionally, molecule coverage increases with increasein attachment temperature as shown in FIG. 11.

Example 2 Electroless Cu Deposition

Following molecule attachment and surface cleaning processes, the epoxysubstrate was subjected to electroless Cu deposition in the followingmanner: (a) immersed in Shipley/Circuposit Conditioner 3320 for 10 minat 65° C. followed by D1 water rinse at 65° C. for 1 min, (b) immersedin Shipley/Cataposit Catalyst 404 (Pre-dip) at 23° C. for 1 min and thenin Shipley/Cataposit Catalyst 44 (Activation) at 40° C. for 5 minfollowed by DI water rinse at 23° C. for 1 min, (c) immersed inShipley/Accelerator 19E (Acceleration) at 30° C. for 5 min followed byDI water rinse at 23° C. for 1 min, (d) immersed in Shipley/Cuposit 328LCopper Mix (E-less Cu) at 30° C. for 10 min followed by DI water rinseat 23° C. for 1 min and blow dry with air at 23° C. for 1 min. Theelectroless film was evaluate by tape peeling shown in FIGS. 12-14 andcharacterized by microscopy shown in FIG. 15. FIGS. 12A and 12Bschematically illustrate the tape peeling test techniques. Tape 500 isplaced and pressed on a portion of a test coupon, in this instance epoxysubstrate 502 having electroless copper 504, formed thereon by methodsof the present invention. A portion of the tape 500 is then peeled offby hand. The tape peeling test gives a qualitative characterization ofthe peel strength of the copper layer and is generally performed to testthe electroless copper layer. FIG. 13 shows photographs of multiple testcoupons 0131 to 0140 of epoxy A substrates having electroless cooperformed thereon by methods of the present invention along with controltest coupon 0007 which was not prepared according to the invention. FIG.14 shows photographs of multiple test coupons 0039 to 0040 of epoxy Bsubstrates having electroless copper formed thereon by methods of thepresent invention along with control test coupon 0026 which was notprepared according to the invention. Test coupons are shown before andafter peeling in both figures. As shown in FIGS. 13 and 14 the porphyrinmolecules of the present invention provide a good substrate for platingand enhance copper adhesion to the smooth epoxy surface. Additionally,better copper coverage is generally achieved with the substratesprepared according to the present invention. FIGS. 15A and 15B furtherillustrate that the porphyrin molecules also reduce the defect densitytherefore promoting the adhesion between copper and epoxy substrate. Asshown in FIG. 15B, both at 50× and 500× magnifications, the copper layeron epoxy B substrates prepared according to the present inventionexhibits good copper adhesion and low defect density, and issignificantly superior to the copper layer prepared conventionally (FIG.15A).

Example 3 Electrolytic Cu Deposition

Electrodeposition was applied to the electroless Cu covered substrate toincrease the thickness of copper up to 25˜50 μm for peel strengthevaluation. The substrate was first cleaned in 1 M sulfuric acid, thenelectroplated in Shipley/Copper Gleam ST-901 Acid Copper at 1 A/dm², 23°C. for 120 min, followed by DI water rinse at 23° C. for 1 min and blowndry with air at 23° C. for 1 min. The sample was then annealed in air at150° C. for 60 min. Next, peel strength is tested on the electrolyticcopper layer. FIGS. 16A and 16B schematically illustrates the peelstrength test technique. First, a peel strip 600 of 10 mm width isprepared by making cuts on the two sides of a test coupon, in thisinstance epoxy substrate 602 having electroless and electrolytic copper604, formed thereon by methods of the present invention. Second, thepeel strip 600 is clamped to the force gauge of a peel tester. Peelstrength is then measured at a 90 degree peel angle and peel speed of 50mm/min. FIG. 17 illustrates that the peel strength of the electrolyticcopper on porphyrin attached surface is increased by a factor of 10compared to the control without molecule attachment.

The foregoing methods and description are intended to be illustrative.In view of the teachings provided herein, other approaches will beevident to those of skill in the relevant arts, and such approaches areintended to fall within the scope of the present invention.

1. A kit for carrying out the binding of metals to a substrate,comprising: a container comprising a heat-resistant organic moleculederivatized with an attachment group Y and a binding group X, thebinding group X promotes binding of metals; and instructional materialsteaching coupling the organic molecule to the substrate by heating themolecule and/or the surface to a temperature of at least 25° C.
 2. Thekit of claim 1 wherein the heat-resistant organic molecule is a surfaceactive moiety.
 3. The kit of claim 2 wherein said surface active moietyis selected from the group consisting of a macrocyclic proligand, amacrocyclic complex, a sandwich coordination complex and polymersthereof.
 4. The kit of claim 3 wherein said surface active moiety is aporphyrin.
 5. The kit of claim 1 wherein the attachment group Y iscomprised of an aryl functional group and/or an alkyl attachment group.6. The kit of claim 5 wherein the aryl functional group is comprised ofa functional group selected from any one or more of: bromo, iodo,hydroxy, ether, hydroxymethyl, formyl, bromomethyl, vinyl, allyl,S-acetylthiomethyl, Se-acetylselenomethyl, ethynyl,2-(trimethylsilyl)ethynyl, mercapto, mercaptomethyl,4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl, and dihydroxyphosphoryl. 7.The kit of claim 5 wherein the alkyl attachment group comprises afunctional group selected from any one or more of: bromo, iodo, hydroxy,ether, formyl, vinyl, mercapto, selenyl, S-acetylthio, Se-acetylseleno,ethynyl, 2-(trimethylsilyl)ethynyl,4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl, and dihydroxyphosphoryl. 8.The kit of claim 1 wherein the attachment group Y is comprised of anyone or more of: amines, alcohols, ethers, other nucleophile, phenylethynes, phenyl allylic groups, phosphonates and combinations thereof.9. The kit of claim 1 wherein the binding group X is comprised of anyone or more of: alcohols, ethers, other nucleophiles, phenyl ethynes,phenyl allylic groups, phosphonates, amines, pyridine; pyrazine;isonicotinamide; imidazole; bipyridine and substituted derivatives ofbipyridine; terpyridine and substituted derivatives; nitriles,isonitriles, thiocyanates, phenanthrolines, substituted derivatives ofphenanthrolines, oxygen, sulfur, phosphorus and nitrogen-donatingligands and combinations thereof.
 10. The kit of claim 1 wherein theheat-resistant organic molecule is carried in a solvent, dispersion,emulsion, paste, or gel.
 11. The kit of claim 1 wherein heat resistantorganic molecule is comprised of a molecule selected from the group of:a porphyrin, a porphyrinic macrocycle, an expanded porphyrin, acontracted porphyrin, a linear porphyrin polymer, a porphyrinic sandwichcoordination complex, or a porphyrin array.